Investments - Schedule of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Marketable Securities [Abstract]
Cost	$ 50,629vrts_MarketableSecuritiesCost	$ 25,937vrts_MarketableSecuritiesCost
Unrealized Loss	(1,353)	(849)
Unrealized Gain	975vrts_MarketableSecuritiesUnrealizedGain	3,880vrts_MarketableSecuritiesUnrealizedGain
Fair Value	50,251us-gaap_MarketableSecurities	28,968us-gaap_MarketableSecurities
Sponsored Funds [Member]
Marketable Securities [Abstract]
Cost	39,079	16,079
Unrealized Loss	(1,190)	(704)
Unrealized Gain	423	2,529
Fair Value	38,312	17,904
Equity Securities [Member]
Marketable Securities [Abstract]
Cost	8,421	7,043
Unrealized Loss	0
Unrealized Gain	319	1,336
Fair Value	8,740	8,379
Sponsored Closed-End Funds [Member]
Marketable Securities [Abstract]
Cost	3,129	2,815
Unrealized Loss	(163)	(145)
Unrealized Gain	233	15
Fair Value	$ 3,199	$ 2,685

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Total debt and equity financial instruments including: (1) securities held-to-maturity, (2) trading securities, and (3) securities available-for-sale.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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-Glossary Trading Securities

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Cost of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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Marketable Securities Cost

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Marketable Securities Unrealized Gain

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Marketable Securities Unrealized Losses

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Trading Securities Unrealized Gain

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Trading Securities Unrealized Loss

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